<img id='img' src='data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/2wBDAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/wAARCAALAAwDAREAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAACAX/xAAmEAAABQMDBAMBAAAAAAAAAAABAgMEBQYREgAHIRMUMUEVIyRh/8QAFgEBAQEAAAAAAAAAAAAAAAAABgcK/8QAJBEAAgEDBAIDAQEAAAAAAAAAAQIRAwQhAAUGEjFBEzJhIlH/2gAMAwEAAhEDEQA/AJUVTlOkQjE3NPQQmThadEt4SPMBE/gov6hAG3r+jz5vrQzRsbQ24anTo9g1VVl1JhHdRgmYgSPREHM5yv8AKt75Gu53DJeXaq/Vj8fdAWK/Ygf7kEmTJ85wraA212Od04i4qel4o0oo5ciJnNPtMRb5FBDtbx1+hjfK9/1dzzqJ8mG6Ut4uUtjT+IdYELgwZA/PBxjONVjg17Uq8bsnu7qq1djVLs6Mzt/XlmaST6kn1jEaFsPuLXEq/aJOqnlU0ui1a9OOXCIT7dq3ZM26WESVkTFJqAIk4vh5ER50zo2dstMAUhA7sAWdgGLBiYZiJLEsT5Jyc6RX9hZ1TUapb0naYkrnxpZUSW0QqY5lHBzvljnWeKqvnBzCi3ARO4eHXXN4CwGUEA9AFx0F3okbjXAJAHUAA+go0k2GxtE2ygq29NQC8AAx9j+6/9k='></img>
<script>
function dataURLtoBlob(dataurl) {
var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {type:mime});
}
function downloadImage(){
var src = document.getElementById('img').src;
var blob= dataURLtoBlob(src);
let url = window.URL.createObjectURL(blob);
let link = document.createElement('a')
link.style.display = 'none'
link.href = url;
link.setAttribute('download', "test.jpg")// 文件名
document.body.appendChild(link)
link.click()
document.body.removeChild(link) // 下载完成移除元素
window.URL.revokeObjectURL(url) // 释放掉blob对象
}
downloadImage();
</script>